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Ariyoshi, Gen; Saruta, Koichi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Maeno, Koki*; Li, Y.*; Tsutsui, Kihei*
Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.1407 - 1420, 2023/08
Cavitation damage on a target vessel due to proton beam-induced pressure waves is one of the crucial issues for the pulsed neutron source using a mercury spallation target. As a mitigation technique for the damage, the helium microbubble injection into the mercury has been carried out by using a swirl bubbler in order to utilize compressibility of bubbles. Moreover, double-walled structure, which consists of an outer wall and an inner wall, has been applied as the target head structure. In this study, we aim to develop an abnormality diagnostic technology to detect the inner wall cracking, which is caused by such cavitation damage, from the outside of the target vessel. The mercury flow fields in the case with the cracking are evaluated by computational fluid dynamics analysis based on finite element method. And then, effect of the cracking on the flow field is discussed from the point of view of the flow-induced vibration and the acoustic vibration.
Miyahara, Shinya*; Arita, Yuji*; Nakano, Keita; Maekawa, Fujio; Sasa, Toshinobu; Obayashi, Hironari; Takei, Hayanori
Nuclear Engineering and Design, 403, p.112147_1 - 112147_17, 2023/03
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)It is important to evaluate the inventories and the release and transport behavior of the spallation products (SPs) in the Lead-Bismuth Eutectic (LBE) coolant system of Accelerator Driven System (ADS) for the safety studies of the radiological hazard both in the cases of normal operation and accident. University of Fukui and JAEA have been developing the computer analysis code TRAIL (Transport of RAdionuclides In Liquid metal systems) which predicts the time dependent behavior of SPs within the LBE coolant system of ADS for the wide range of operational events. The source term of both radioactive and stable SPs in the LBE coolant is given as input and the radioactive decay chain model for the radioactive SPs is implemented in the code to evaluate the effect of precursors on the SPs mobility. This paper presents the recent advancement status of the code development and the validation results comparing with the distribution data of volatile SPs in MEGAPIE spallation target.
Ariyoshi, Gen; Obayashi, Hironari; Sasa, Toshinobu
Journal of Nuclear Science and Technology, 59(9), p.1071 - 1088, 2022/09
Times Cited Count：1 Percentile：31.61(Nuclear Science & Technology)Electromagnetic induction method is one of the effective techniques for local velocity measurement in heavy liquid metals. Ricou and Vives' probe and Von Weissenfluh's probe are famous instrumentations using a permanent magnet. However, sensitivity and measurement volume of the probes show unexpected variation since demagnetization of the magnet is occurred by temperature increase up to the Curie temperature. In this study, electromagnetic probe incorporating a miniature electromagnet was newly developed to overcome such unexpected variation. The diameter and the length of the sensor was 6 mm and 155 mm, respectively. The sensitivity and the measurement volume of the probe were assessed by measurement of local velocity of flowing mercury in a square channel. To clarify the validity for the measured velocity profiles, numerical velocity profiles were calculated and compared with experiment. And the validity for the measured velocity profiles were confirmed by calculated result.
Naoe, Takashi; Kinoshita, Hidetaka; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro
JAEA-Technology 2022-018, 43 Pages, 2022/08
JAEA-Technology-2022-018.pdf:7.84MB
In the liquid mercury target system for the pulsed spallation neutron source of Materials and Life science experimental Facility (MLF) at the Japan in the Japan Proton Accelerator Research Complex (J-PARC), cavitation that is generated by the high-energy proton beam-induced pressure waves, resulting severe erosion damage on the interior surface of the mercury target vessel. The erosion damage is increased with increasing the proton beam power, and has the possibility to cause the leakage of mercury by the penetrated damage and/or the fatigue failure originated from erosion pits during operation. To achieve the long term stable operation under high-power proton beam, the mitigation technologies for cavitation erosion consisting of surface modification on the vessel interior surface, helium gas microbubble injection, double-walled beam window structure has been applied. The damage on interior surface of the vessel is never observed during the beam operation. Therefore, after the target operation term ends, we have cut out specimen from the target nose of the target vessel to inspect damaged surface in detail for verification of the cavitation damage mitigation technologies and lifetime estimation. We have developed the techniques of specimen cutting out by remote handling under high-radiation environment. Cutting method was gradually updated based on experience in actual cutting for the used target vessel. In this report, techniques of specimen cutting out for the beam entrance portion of the target vessel in high-radiation environment and overview of the results of specimen cutting from actual target vessels are described.
Sasa, Toshinobu
Purazuma, Kaku Yugo Gakkai-Shi, 98(5), p.211 - 215, 2022/05
Lead-bismuth eutectic (LBE) alloy is promising as a spallation target for next-generation reactor coolants and accelerator drive systems (ADS) due to its nuclear and chemical properties. LBE is a heavy metal, and it has good properties both as a spallation target and as a coolant for nuclear transmutation systems of long-lived radioactive nuclei. On the other hand, to improve compatibility with structural materials is one of the major issues in its utilization. The latest research results such as high-temperature operation of LBE and oxygen concentration control to ensure corrosion resistance with the aim of early commercialization of nuclear conversion technology by ADS is introduced.
Obayashi, Hironari; Yamaki, Kenichi*; Yoshimoto, Hidemitsu*; Kita, Satoshi*; Wan, T.*; Sasa, Toshinobu
JAEA-Technology 2021-035, 66 Pages, 2022/03
JAEA-Technology-2021-035.pdf:4.26MB
Construction of Transmutation Experimental Facility (TEF) is under planning in Japan Proton Accelerator Research Complex (J-PARC) program to promote R&Ds on realization of transmutation technology by an accelerator driven system (ADS). As a facility of TEF, ADS Target Test Facility (TEF-T) will provide a spallation target to study target technology and perform post irradiation examination (PIE) of candidate materials of ADS. In ADS, lead-bismuth eutectic (LBE) alloy is used as a spallation target material and a core coolant. As is well known, LBE has corrosive to structural materials hence each component of the target system should provide compatibility with LBE. In addition, instrumentations for LBE are restricted by the target operation condition such as high temperature and irradiation environment. The devices for LBE have been developed individually to achieve the LBE target system. "Integrated Multi-functional MOckup for TEF-T Real-scale TArget Loop, IMMORTAL" was fabricated as a mock-up test loop of the target for the purpose of the integration testing of individually developed devices. This report describes an overview of IMMORTAL and the design of the installed devices.
Teshigawara, Makoto; Nakamura, Mitsutaka; Kinsho, Michikazu; Soyama, Kazuhiko
JAEA-Technology 2021-022, 208 Pages, 2022/02
JAEA-Technology-2021-022.pdf:14.28MB
The Materials and Life science experimental Facility (MLF) is an accelerator driven pulsed spallation neutron and muon source with a 1 MW proton beam. The construction began in 2004, and we started beam operation in 2008. Although problems such as exudation of cooling water from the target container have occurred, as of April 2021, the proton beam power has reached up to 700 kW gradually, and stable operation is being performed. In recent years, the operation experience of the rated 1 MW has been steadily accumulated. Several issues such as the durability of the target container have been revealed according to the increase in the operation time. Aiming at making a further improvement of MLF, we summarized the current status of achievements for the design values, such as accelerator technology (LINAC and RCS), neutron and muon source technology, beam transportation of these particles, detection technology, and neutron and muon instruments. Based on the analysis of the current status, we tried to extract improvement points for upgrade of MLF. Through these works, we will raise new proposals that promote the upgrade of MLF, attracting young people. We would like to lead to the further success of researchers and engineers who will lead the next generation.
Harada, Masahide; Teshigawara, Makoto; Oi, Motoki; Oikawa, Kenichi; Takada, Hiroshi; Ikeda, Yujiro
Nuclear Instruments and Methods in Physics Research A, 1000, p.165252_1 - 165252_8, 2021/06
Times Cited Count：2 Percentile：34.88(Instruments & Instrumentation)This study explores high-energy neutron components of the extracted neutron beam at J-PARC pulsed neutron source using the foil activation method with threshold reactions. Foils of aluminum, gold, bismuth, niobium, and thulium were used to cover the neutron energy range from 0.3 MeV to 79.4 MeV. The experiment was performed using neutron beams of BL10 (NOBORU). The foils were irradiated by a neutron beam at 13.4 m from the moderator. To characterize high-energy neutron fields for irradiation applications, reaction rates in three different configurations with and without B
C slit and Pb filter were examined. To compare the experiments with calculations given for the user, reaction rates for corresponding reactions were calculated by the PHITS code with the JENDL-3.2 and the JENDL dosimetry file. Although there was a systematic tendency in C/E (Calculation/Experiment) ratios for different threshold energies, which C/E ratio decreased as threshold energy increased up to 100 MeV, and all C/E ratios were in the range of 1.0
0.2. This indicated that high-energy neutron calculations were adequate for the analysis of experimental data for NOBORU users.
Kasugai, Yoshimi; Sato, Koichi; Takahashi, Kazutoshi*; Miyamoto, Yukihiro; Kai, Tetsuya; Harada, Masahide; Haga, Katsuhiro; Takada, Hiroshi
JPS Conference Proceedings (Internet), 33, p.011144_1 - 011144_6, 2021/03
A spallation neutron source with a mercury target has been in operation at the Materials and Life Science Experimental Facility of J-PARC since 2008. The target vessel made of stainless steel is required to be exchanged periodically due to radiation damage etc. In this presentation, tritium gas release observed in the first series of exchange work in 2011 and the analytical results will be shown.
Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei*; Haga, Katsuhiro; Shimada, Tsubasa*; Kanomata, Kenichi*
Materials Science Forum, 1024, p.145 - 150, 2021/03
To realize a high beam power operation at the J-PARC, a mercury target vessel covered with water shroud was developed. In the first step, to realize an operation at 500 kW, the basic structure of the initial design was followed and the connection method between the mercury vessel and the water shroud was changed. Additionally, the operation at a beam power of 500 kW was realized in approximately eight months. In the second step, to realize the operation at 1 MW, the new structure in which only rear ends of vessels were connected was investigated. Cooling of the mercury vessel is used to reduce thermal stress and thick vessels of the water shroud are used to increase stiffness for the internal pressure; therefore, it was adopted. The stress in each vessel was lower than the allowable stress based on the pressure vessel code criteria prescribed in the Japan Industrial Standard, and confirmation was obtained that the operation with a beam power of 1 MW could be conducted.
for a mercury target induced by 3-GeV protonsMatsuda, Hiroki; Iwamoto, Hiroki; Meigo, Shinichiro; Takeshita, Hayato*; Maekawa, Fujio
Nuclear Instruments and Methods in Physics Research B, 483, p.33 - 40, 2020/11
Times Cited Count：3 Percentile：36.4(Instruments & Instrumentation)A thick target neutron yield for a mercury target at an angle of 180 from the incident beam direction is measured with the time-of-flight method using a 3-GeV proton beam at the Japan Proton Accelerator Research Complex (J-PARC). Comparing the experimental result with a Monte Carlo particle transport simulation by the Particle and Heavy Ion Transport code System (PHITS) shows that there are apparent discrepancies. We find that this trend is consistent with an experimental result of neutron-induced re- action rates obtained using indium and niobium activation foils. Comparing proton-induced neutron-production double-differential cross-sections for a lead target at backward directions between the PHITS calculation and experimental data suggests that the dis- crepancies for our experiments would be linked to the neutron production calculation around 3 GeV by the PHITS spallation model and/or the calculation of nonelastic cross-sections around 3 GeV in the particle transport simulation.
Matsuda, Hiroki; Meigo, Shinichiro; Iwamoto, Hiroki; Maekawa, Fujio
EPJ Web of Conferences, 239, p.06004_1 - 06004_4, 2020/09
Times Cited Count：1 Percentile：72.93(Nuclear Science & Technology)For the Accelerator-Driven nuclear transmutation System (ADS), nuclide production yield estimation in the lead-bismuth target is important to manage the target. However, experimental data of nuclide production yield by spallation and high-energy fission reactions are scarce. In order to obtain the experimental data, we experimented in J-PARC using 
Pb and 
Bi samples. The samples were irradiated with protons at various kinematic energy points between 0.4 and 3.0 GeV. After the irradiation, the nuclide production cross section over 
Be to 
Re was obtained by spectroscopic measurement of decay gamma-rays from the samples with HPGe detectors. The present experimental results were compared with the evaluated data (JENDL-HE/2007) and the calculation with the PHITS code and the INCL++ code. The present experiment data showed consistency with other experimental data with better accuracy than other ones. In reactions to produce light nuclides, JENDL and calculation with the PHITS and INCL++ for Be production agreed with the data.
Na production, however, underestimated about 1/10 times. For middle to heavy nuclide productions cases, both calculations agreed with the experiment by a factor of two. JENDL showed lower energy having a maximum value of excitation function maximal value than the experimental data.
Iwamoto, Hiroki; Meigo, Shinichiro
Journal of Nuclear Science and Technology, 57(3), p.276 - 290, 2020/03
Times Cited Count：2 Percentile：24.28(Nuclear Science & Technology)This paper presents an approach to uncertainty estimation of spallation particle multiplicity of lead (
Pb), primarily focusing on proton-induced spallation neutron multiplicity (
) and its propagation to a neutron energy spectrum. The uncertainty is estimated from experimental proton-induced neutron-production double-differential cross sections (DDXs) and model calculations with the Particle and Heavy Ion Transport code System (PHITS). Uncertainties in multiplicities for 
, 
, and 
reactions are then inferred from the estimated uncertainty and the PHITS calculation. Using these uncertainties, uncertainty in a neutron energy spectrum produced from a thick Pb target bombarded with 500 MeV proton beams, measured in a previous experiment, is quantified by a random sampling technique, and propagation to the neutron energy spectrum is examined. Relatively large uncertainty intervals (UIs) were observed outside the lower limit of the measurement range, which is prominent in the backward directions. Our findings suggest that a reliable assessment of spallation neutron energy spectra requires systematic DDX experiments for detector angles and incident energies below 100 MeV as well as neutron energy spectrum measurements at lower energies below 
1.4 MeV with an accuracy below the quantified UIs.
Takada, Hiroshi; Haga, Katsuhiro
JPS Conference Proceedings (Internet), 28, p.081003_1 - 081003_7, 2020/02
At the Japan Proton Accelerator Research Complex (J-PARC), the pulsed spallation neutron source has been in operation with a redesigned mercury target vessel from October 2017 to July 2018, during which the operational beam power was restored to 500 kW and the operation with a 1-MW equivalent beam was demonstrated for one hour. The target vessel includes a gas-micro-bubbles injector and a 2-mm-wide narrow mercury flow channel at the front end as measures to suppress the cavitation damage. After the operating period, it was observed that the cavitation damage at the 3-mm-thick front end of the target vessel could be suppressed less than 17.5 
m.
Katano, Ryota; Yamanaka, Masao*; Pyeon, C. H.*
Journal of Nuclear Science and Technology, 57(2), p.169 - 176, 2020/02
Times Cited Count：4 Percentile：41.24(Nuclear Science & Technology)We proposed the linear combination method as a subcriticality measurement method which estimates the prompt neutron decay constant (
) correlated with the subcriticality using measurement results obtained at multiple detector positions. In the previous study, we confirmed applicability of the linear combination method through the pulsed neutron experiment with DT neutron source at Kyoto University Critical Assembly (KUCA). In this study, we conduct the pulsed neutron source experiment with spallation neutrons at KUCA and confirm the robustness of the linear combination to neutron sources.
Miyahara, Shinya*; Ohdaira, Naoya*; Arita, Yuji*; Maekawa, Fujio; Matsuda, Hiroki; Sasa, Toshinobu; Meigo, Shinichiro
Nuclear Engineering and Design, 352, p.110192_1 - 110192_8, 2019/10
Times Cited Count：5 Percentile：48.99(Nuclear Science & Technology)Lead-Bismuth Eutectic (LBE) is used as a spallation neutron target and coolant materials of Accelerator Driven System (ADS), and many kinds of elements are produced as spallation products. It is important to evaluate the release and transport behavior of the spallation products in the LBE. The inventories and the physicochemical composition of the spallation products produced in LBE have been investigated for an LBE loop in the ADS Target Test Facility (TEF-T) in J-PARC. The inventories of the spallation products in the LBE were estimated using the PHITS code. The physicochemical composition of the spallation products in the LBE was calculated using the Thermo-Calc code under the conditions of the operation temperatures of LBE from 350C to 500C and the oxygen concentrations in LBE from 10 ppb to 1 ppm. The calculation showed that the 5 elements of Rb, Tl, Tc, Os, Ir, Pt, Au and Hg were soluble in LBE under the all given conditions and any kinds of compound were not formed in LBE. It was suggested that the oxides of Ce, Sr, Zr and Y were stable as CeO
, SrO, ZrO and YO
in the LBE.
Aso, Tomokazu; Tatsumoto, Hideki*; Otsu, Kiichi*; Kawakami, Yoshihiko*; Komori, Shinji*; Muto, Hideki*; Takada, Hiroshi
JAEA-Technology 2019-013, 77 Pages, 2019/09
JAEA-Technology-2019-013.pdf:5.59MB
At Materials and Life Science experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), a 1-MW pulsed spallation neutron source is equipped with a cryogenic hydrogen system which circulates liquid hydrogen (20 K and 1.5 MPa) to convert high energy neutrons generated at a mercury target to cold neutrons at three moderators with removing nuclear heat of 3.8 kW deposited there. The cryogenic system includes an accumulator with a bellows structure in order to absorb pressure fluctuations generated by the nuclear heat deposition in the system. Welded inner bellows of the first accumulator was failured during operation, forcing us to improve the accumulator to have sufficient pressure resistance and longer life-time. We have developed elemental technologies for manufacturing welded bellows of the accumulator by a thick plate with high pressure resistance, succeeding to find optimum welding conditions. We fabricated a prototype bellows block and carried out an endurance test by adding a pressure change of 2 MPa repeatedly. As a result, the prototype bellows was successfully in use exceeding the design life of 10,000 times. Since distortions given during welding and assembling affect functionality and lifetime of the bellows, we set the levelness of each element of the bellows as within 0.1. The improved accumulator has already been in operation for about 25,000 hours as of January 2019, resulting that the number of strokes reached to 16,000. In July 2018, we demonstrated that the accumulator could suppress the pressure fluctuation generated by the 932 kW beam injection as designed. As current operational beam power is 500 kW, the current cryogenic hydrogen system could be applicable for stable operation at higher power in the future.
Wakui, Takashi; Ishii, Hideaki*; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Wakai, Eiichi; Takada, Hiroshi; Futakawa, Masatoshi
Materials Transactions, 60(6), p.1026 - 1033, 2019/06
Times Cited Count：3 Percentile：17.96(Materials Science, Multidisciplinary)The mercury target has large size as 1.3
1.32.5 m
. In view of reducing the amount of wastes, we studied the structure so that the fore part could be separated. The flange is required to have high seal performance less than 110
Pa m/s. Invar with low thermal expansion is a candidate. Due to its low stiffness, however, the flange may deform when it is fastened by bolts. Practically invar is reinforced with stainless steel where all interface between them has to be bonded completely with the HIP bonding. In this study, we made specimens at four temperatures and conducted tensile tests. The specimen bonded at 973 K had little diffusion layer, and so fractured at the interface. The tensile strength reduced with increasing the temperature, and the reduced amount was about 10% at 1473 K. The analyzed residual stresses near the interface increased by 50% at maximum. Then, we concluded that the optimum temperature was 1173 K.
Iwamoto, Hiroki; Meigo, Shinichiro
Journal of Nuclear Science and Technology, 56(2), p.160 - 171, 2019/02
Times Cited Count：3 Percentile：31.89(Nuclear Science & Technology)We present a new model to describe the fission probability of the high-energy fission model, as deduced from the intranuclear cascade calculation with the Intra-Nuclear Cascade model of Li
ge (INCL) version 4.6 and Prokofiev's phenomenological systematics of the proton-induced fission cross sections. This model is implemented in the de-excitation model of the Generalized Evaporation Model (GEM), and applied to Monte Carlo spallation reaction simulation using the Particle and Heavy Ion Transport code System (PHITS). Comparing with experimental data for subactinide nuclei shows that this model can provide a unified prediction of the proton-, neutron-, and deuteron-induced fission cross sections with markedly improved accuracy. The calculated fission fragments tend to shift to higher mass numbers. To account for the isotopic distributions of fission fragments within the framework of a coupled INCL/GEM, modification of INCL is required, especially for description of the highly-excited states of residual nuclei.
Wan, T.; Naoe, Takashi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Obayashi, Hironari; Sasa, Toshinobu
Materials, 12(4), p.681_1 - 681_15, 2019/02
Times Cited Count：3 Percentile：17.96(Chemistry, Physical)